1. Field of the Invention
The present invention relates to an EL element and a display using the same.
2. Background Art
First Aspect of the Invention
EL elements (electroluminescent elements) are self-luminous elements and are quick in response and are excellent in visibility of images, as well as in image display characteristics of moving images. In particular, organic EL elements can emit light under direct current and low voltage conditions and thus are expected to find extensive applications.
The EL element generally comprises a glass substrate and a first electrode, an EL part, a second electrode, and a protective layer stacked in that order on the glass substrate. From the viewpoint of improving the function of the protective layer, however, an EL element has been developed in which, as with the glass substrate, the protective layer is formed of glass and a sealant layer is provided on the peripheral part between both the glass parts for sealing. On the other hand, in recent years, an attempt has been made to use a film substrate instead of the glass substrate. For example, Japanese Patent Laid-Open No. 15859/2002 proposes an EL element that comprises a film substrate, a first electrode, an organic EL layer, a second electrode, and a protective layer stacked on top of one another, the protective layer being formed of a layer of aluminum, silicon oxide or the like, or formed of an SiN film formed by sputtering.
From the viewpoint of improving the protective function of the protective layer, however, when the protective layer is formed of the same member as the film substrate, as in the case of the construction using the glass substrate, the formation of a sealant layer on the peripheral part of upper and lower film substrates results in the presence of a sealant layer-formed area and a sealant layer-unformed area. For this reason, mechanical properties such as rigidity and thermal expansion of the EL element are heterogeneous. Further, in this case, the distance between the upper and lower film substrates cannot be kept constant, and, thus, the planarity of the surface of the EL element cannot be sometimes maintained. Further, upon rolling of the whole EL element, the upper and lower film substrates come close to each other, and, consequently, the EL part comprising the first electrode, the EL layer, the second electrode and the like sandwiched between them is pressed and is sometimes damaged.
Second Aspect of the Invention
EL elements (electroluminescent elements) are self-luminous elements and are quick in response. Further, the thickness of the EL elements is, per se, small. Therefore, these EL elements are utilized as displays that can display letters or pictures.
For example, Japanese Patent Laid-Open Nos. 13898/2001 and 15264/2001 propose a display comprising an EL element which comprises two synthetic resin sheets for realizing further thickness reduction and flexibility improvement purposes. In these displays, however, since the EL element is sealed at its outer peripheral part, in the EL element, a sealed outer peripheral part and an unsealed part are present. This poses the following disadvantages. Mechanical properties such as rigidity and thermal expansion of the EL element are rendered uneven. Further, the distance between the two synthetic resin sheets cannot be kept constant making it impossible to maintain the planarity of the surface of the EL element. When the display is applied in a curved form, the first electrode, the EL layer, the second electrode and the like constituting the EL element sandwiched between the two synthetic resin sheets are pressed and are damaged.
Further, the display proposed in Japanese Patent Laid-Open No. 13898/2001 is in the form of a resin film formed by properly combining posters, letters, and pictures and rendering the necessary part transparent or semi-transparent. The display proposed in Japanese Patent Laid-Open No. 15264/2001 comprises a substrate and a luminescent pattern formed by forming a light shielding part by printing or the like to pattern the luminescent part on the surface of the substrate. Due to the above constructions, in these displays, letters or pictures which can be displayed are restricted making it difficult to realize displays with a free design.